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  • 5-Fluorouracil

    Would you please comment on the recent letter in annals of oncology Volume 23 No. 2, pages 543-544, regarding the absence of 5-FU in the milk of a woman being treated for rectal carcinoma, despite normal plasma pharmacokinetics. i notice it does not discuss the metabolites of 5-FU. Would you expect the transfer to be similar? Would this information, although clearly based on only one woman, make breastfeeding with careful monitoring of the infant more reasonable?
    My sister, recently diagnosed with a gastric adenocarcinoma, will begin chemotherapy with 5-FU and leucovorin in the next few weeks.
    She is nursing a nearly 5 month old infant who, to date has absolutely refused all alternative sources of nutrition, including pumped breast milk. Out of desperation he was wet nursed by family and friends during her surgery (this would be more challenging long term), so she is anxious to carefully consider all available information before making a decision to wean.
    Are assays of this type readily available at a university center?
    Thanks for your thoughts. Family physician, Vancouver

  • #2

    Having reviewed this brief report, I am still a little uncomfortable that we may not know all the facts about this hazardous drug. As you suggested, its the metabolites of 5FU that are probably active (fluorodeoxyuridine monophosphate (FdUMP)), and we do not apparently know their levels in the maternal plasma, or milk for that matter.

    I'd suggest we hold off judgement on this papers results until we know a lot more. I'd also suggest she not breastfeed while taking this medication. Sorry, but there are times when breastfeeding may be more risky than formula-feeding. She could always pump and discard her milk to sustain her milk supply, and then reintroduce breastfeeding after the treatment.

    Tom Hale Ph.D.


    • #3
      Thanks Dr. Hale.
      If she is to do 5 4 week cycles, mostly starting with 5-FU given on the first 5 days (or slight modifications in the cycles with radiation), how long would be expected until the drug and it's metabolites are out of her milk. Could she nurse for, say, the last 10-14 days of each cycle. i realize this depends on the half life of the metabolites and not just the FU which is quite short. Thank you.